Intravaginal Ring Core-Sheath Structure for Independent Steroid Release

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Solution Overview

Problem

Existing intravaginal rings face challenges in controlling the simultaneous and independent release of multiple drugs, particularly estrogenic and progestational steroids, due to complex manufacturing processes, dose dumping, and variability in release rates, which complicates achieving a desired delivery ratio and optimal physiological release profiles.

Innovation Solution

The intravaginal ring design incorporates a core of ethylene-vinyl acetate copolymer with a vinyl acetate content of 26-40 wt% and an estrogenic steroid, surrounded by a sheath of ethylene-vinyl acetate copolymer with 20-40 wt% and a high concentration of progestational steroid, up to 40 wt%, to achieve a substantially zero-order release of both steroids independently.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a blend of drugs is placed in a single intravaginal ring in proportion equal to the desired delivery rate ratio, then the device structure is simplified, but the drugs will not diffuse together through the surface or membrane at the same ratio due to different inherent permeation rates

Engineering Contradiction:

Improvedevice structureVSAvoiddelivery rate ratio control

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The intravaginal ring is divided into multiple compartments, each containing a different drug. This segmentation allows each drug to be delivered at its desired rate independently, overcoming the problem of different permeation rates while maintaining a single device structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the intravaginal ring (compartments) are assigned different drug formulations and release characteristics tailored to the specific requirements of each drug, enabling precise control of delivery rate ratios through localized optimization rather than uniform composition.

Inventive Principle:

Principle #3Local quality

2Manufacturing precision

If two or more separate intravaginal rings are used to maintain specified delivery rate ratios for multiple drugs, then the delivery control is improved, but the disruption to normal physiological activity increases and the device complexity increases

Engineering Contradiction:

Improvedelivery rate ratio controlVSAvoidphysiological disruption

Core Design Contradiction:

Manufacturing precisionVSEase of operation

Solution Approach 1:

Multiple drug delivery functions that would traditionally require separate intravaginal rings are merged into a single multi-compartment device. This combination maintains precise delivery rate control for each drug while reducing the number of devices the user must manage and minimizing physiological disruption.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The intravaginal ring is designed as a multi-functional device capable of delivering multiple drugs simultaneously at controlled rates, replacing the need for multiple single-function devices and providing comprehensive therapy through a single insertion.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Manufacturing precision

If reservoir systems with a drug loaded core and non-medicated membrane are used, then zero order release is achieved when the reservoir is saturated, but the release rate decreases when drug concentration in the reservoir falls and the system is difficult to fabricate reliably

Engineering Contradiction:

Improverelease rate controlVSAvoidrelease rate consistency

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The membrane properties are modified by incorporating hydrophilic polymers that change the diffusion characteristics. This parameter change allows the system to maintain zero-order release kinetics throughout the drug delivery period by controlling the water permeability and drug diffusion rate through the membrane, preventing the release rate decrease that occurs in traditional reservoir systems.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This design ensures stable, controlled, and simultaneous release of estrogenic and progestational steroids over an extended period, minimizing initial burst and manufacturing complexity, while maintaining a consistent release rate for up to three months.

Implementation Method 1

diffusion through the surface of the ring

Methodology Applied

Scientific EffectDiffusion: Diffusion

Implementation Method 2

the drug first partitions into the sheath from the reservoir

Methodology Applied

Scientific EffectPartitioning: Absorption (physical)

Data Source

PatentUS20250295582A1Intravaginal ring

Publication Date: 2025.09.25 SEVER PHARMA SOLUTIONS

AI summary

The present invention relates to an intravaginal ring (1) a core (2) comprising a first ethylene-vinyl acetate copolymer (3) having a vinyl acetate content from 28 to 40 wt %, and at least 10 wt % of an estrogenic steroid (4) based on the weight of the core, and a sheath (5) comprising a second ethylenevinyl acetate copolymer (6) having a vinyl acetate content from 18 to 28 wt %, and at least 10 wt % of a progestational steroid (7) based on the weight of the sheath. Using the intravaginal ring according to the present the inventors have found that it is possible to attain independent and optimal release of the two active ingredients: an estrogenic steroid and a progestational steroid, without the need for complex assembly of parts and without the need to use sophisticated multi-layer extrusion technology.